The present invention relates to a projection head lamp of the type in which light beams reflected by a substantially elliptical reflector are projected forward by a projection lens. More particularly, the invention relates to a projection head lamp for vehicles capable of selectively changing a beam distribution pattern from one pattern to another by turning a shade with a blade-like shade plate.
An example of this type of head lamp is disclosed in Unexamined Japanese Utility Model Application (OPI) No. Sho. 63-41801, for example. The disclosed head lamp is constructed as shown in FIG. 1. As shown, a light source 3 is positioned at the first focal point F1 of a reflector 2 shaped substantially elliptical, and a shade 4 is positioned at the second focal point F2. The shade 4 is constructed with a body 8 including gears, and a shade plate 9 extended outward from the body 8. In the head lamp thus constructed, for selectively changing a beam distribution pattern from one beam pattern to another, the shade 4 is turned about a horizontal support shaft O, to shade part of light beams directed toward a projection lens 5. Reference numeral 1 designates a lamp body, and numeral 6, a front lens.
Another head lamp of this type has been proposed. The shade structure of the head lamp contains a plural number of shade plates 9, as shown in FIG. 2. However, this proposal suffers from the following disadvantages.
In the head lamp having such a shade structure, to change a beam distribution pattern, a shade 4 is turned. During the process of turning the shade 4, the position of the top end of the shade plate 9 is remarkably lowered. As a result, a state that the top end of the shade plate 9 is not in a predetermined position (near to the second focal point F2) occurs for an instant. At this time, the beam distribution pattern resembles the main beam distribution pattern. The head lamp gives a glare to the driver in the vehicle running in the opposite direction. The driver in the forerunning vehicle mistakenly recognizes light of that beam pattern as the sign of passing.